High resistivity compositions

ABSTRACT

The present invention relates to a black matrix formed by applying a curable coating composition onto a substrate to form a curable coating, curing the curable coating imagewise to form a coating, and developing and drying the coating. The curable coating composition comprises a vehicle, a curable resin, and at least one modified pigment comprising a pigment having attached at least one organic group having the formula —X—I or —X—NI, wherein X, which is directly attached to the pigment, represents an arylene or heteroarylene group, an alkylene group, an aralkylene group, or an alkarylene group, I represents a non-polymeric group comprising at least one ionic group or at least one ionizable group, and NI represents a non-polymeric group comprising at least one nonionic group. The curable coating composition, curable coating, and cured coating are also described. Also disclosed is a method of controlling the resistivity of a coating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional PatentApplication Nos. 60/619,317, filed Oct. 15, 2004, 60/645,972, filed Jan.11, 2005, 60/698,204, filed Jul. 7, 2005, 60/708,000, filed Aug. 12,2005, and 60/715,877, filed Sep. 9, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to black matrixes prepared from a curablecoating composition. The present invention also relates to the curablecoating composition, to curable coatings prepared from the curablecoating composition, and coatings prepared by curing the curablecoatings. The present invention further relates to methods of preparingcurable coatings having preselected electrical properties.

2. Description of the Related Art

Black matrix is a generic name for materials used in color displays toimprove the contrast of an image by separating individual color pixels.In liquid crystal displays (LCDs), the black matrix is a thin filmhaving high light-shielding capability and is formed between the threecolor elements of a color filter. In LCD's using thin film transistors(TFT), the black matrix also prevents the formation of photo-inducedcurrents due to reflected light in the TFT.

The black matrix layer in liquid crystal displays has been manufacturedby vapor deposition of Cr/CrO. Although chromium based films haveexcellent light-shielding capabilities, the metal vapor depositionprocess is expensive. In addition, chromium use and disposal is subjectto increasingly restrictive environmental regulations. Chromium filmsalso have low resistivity, which restricts the electrical design of LCDsto a subset of the possible design configurations.

Black pigments such as carbon black have been used in polymercompositions to make resistive black matrixes. However, typical systemshave not been able to provide the desired balance of overall properties.For example, while a black matrix containing a carbon black pigmentcould provide the required light-shielding capabilities (that is, anoptical density (OD) of greater than 3 at 1 micron thickness), typicallythe film would have only a modest resistivity. Alternatively, if ahighly resistive film were produced, the OD would typically be low.

Modified pigments having attached organic groups have also beendisclosed for use in a black matrix for color filters. For example, U.S.Patent Publication No. 2003-0129529 A1 discloses, in part, a blackmatrix prepared using a modified pigment comprising a pigment havingattached at least one polymeric group, wherein the polymeric groupcomprises at least one photopolymerizable group and at least one ionicor ionizable group. Also, U.S. Patent Publication No. 2002-0020318 A1discloses, in part, a black matrix prepared using a modified pigmentcomprising a pigment having attached at least one organic ionic groupand at least one amphiphilic counterion. In addition, U.S. PatentPublication No. 2002-0011185 A1 discloses, in part, the use of amodified pigment comprising a pigment having attached at least onealkylene or alkyl group having 50-200 carbons. While these materialsprovide black matrixes and dispersions with good overall performance,there remains a need for black matrixes with improved properties, inparticular, resistivity and optical density.

SUMMARY OF THE INVENTION

The present invention relates to a black matrix comprising at least onemodified pigment, wherein the modified pigment comprises a pigmenthaving attached at least one organic group having the formula —X—I or—X—NI, wherein X, which is directly attached to the pigment, representsan arylene or heteroarylene group, an alkylene group, an aralkylenegroup, or an alkarylene group, I represents a non-polymeric groupcomprising at least one ionic group or at least one ionizable group, andNI represents a non-polymeric group comprising at least one nonionicgroup. Preferably, the black matrix is formed by applying a curablecoating composition onto a substrate to form a curable coating, curingthe curable coating imagewise to form a coating, and developing anddrying the coating. The curable coating composition comprises a vehicleand the modified pigment.

The present invention further relates to a curable coating compositioncomprising a vehicle, a curable resin and at least one modified pigment,wherein the modified pigment comprises a pigment having attached atleast one organic group having the formula —X—I or —X—NI, wherein X,which is directly attached to the pigment, represents an arylene orheteroarylene group, an alkylene group, an aralkylene group, or analkarylene group, I represents a non-polymeric group comprising at leastone ionic group or at least one ionizable group, and NI represents anon-polymeric group comprising at least one nonionic group. The modifiedpigment is present in an amount such that, when the curable coatingcomposition is applied to a substrate to form a curable coating andcured to form a coating, the coating comprises greater than or equal toabout 30 wt % of the modified pigment based on the total weight of thecoating.

The present invention further relates to a curable coating comprising acurable resin and at least one modified pigment, wherein the modifiedpigment comprises a pigment having attached at least one organic grouphaving the formula —X—I or —X—NI, wherein X, which is directly attachedto the pigment, represents an arylene or heteroarylene group, analkylene group, an aralkylene group, or an alkarylene group, Irepresents a non-polymeric group comprising at least one ionic group orat least one ionizable group, and NI represents a non-polymeric groupcomprising at least one nonionic group. The modified pigment is presentin an amount such that, when the curable coating is cured to form acoating, the coating comprises greater than or equal to about 30 wt % ofthe modified pigment based on the total weight of the coating.

The present invention further relates to a black matrix formed byapplying a curable coating composition onto a substrate to form acurable coating, curing the curable coating imagewise to form a coating,and developing and drying the coating. The curable coating compositioncomprises a vehicle and at least one modified pigment, wherein themodified pigment comprises the reaction product of a pigment, such ascarbon black, and a persulfate reagent. The present invention furtherrelates to a curable coating composition comprising a curable resin andthis modified pigment, wherein the modified pigment is present in anamount such that, when the curable coating composition is applied to asubstrate to form a curable coating and cured to form a coating, thecoating comprises greater than or equal to about 30 wt % of the modifiedpigment based on the weight of the coating. The present inventionfurther relates to a curable coating comprising a curable resin and thismodified pigment, wherein the modified pigment is present in an amountsuch that, when the curable coating is cured to form a coating, thecoating comprises greater than or equal to about 30 wt % of the modifiedpigment based on the total weight of the coating.

The present invention further relates to a coating comprising a resinand at least one modified pigment. In one embodiment, the modifiedpigment of the coating comprises a pigment having attached at least oneorganic group having the formula —X—I or —X—NI, wherein X, which isdirectly attached to the pigment, represents an arylene or heteroarylenegroup, an alkylene group, an aralkylene group, or an alkarylene group, Irepresents a non-polymeric group comprising at least one ionic group orat least one ionizable group, and NI represent a non-polymeric groupcomprising at least one nonionic group. In another embodiment, thecoating comprises a resin and at least one modified pigment and has avolume resistivity of greater than or equal to 10¹² ohm-cm and anoptical density of greater than or equal to 3 at a 1 micron thickness.In a third embodiment, the coating comprises a resin and at least onemodified pigment and has a volume resistivity of between 10⁶ and 10⁸ohm-cm and an optical density of greater than or equal to 4 at a 1micron thickness. In a fourth embodiment, the coating comprises a resinand at least one modified pigment, wherein the modified pigment is thereaction product of a pigment, such as carbon black, and a persulfatereagent. For each of these embodiments, the coating comprises greaterthan or equal to about 30 wt % of the modified pigment based on thetotal weight of the coating.

The present invention further relates to a method of controlling theresistivity of a coating comprising a resin and a pigment. The methodcomprises the step of preparing a curable coating composition comprisinga vehicle, a curable resin, and at least one modified pigment. Themodified pigment comprises the pigment having attached at least oneorganic group having the formula —X—I or —X—NI, wherein X, which isdirectly attached to the pigment, represents an arylene or heteroarylenegroup, an alkylene group, an aralkylene group, or an alkarylene group, Irepresents a non-polymeric group comprising at least one ionic group orat least one ionizable group, and NI represent a non-polymeric groupcomprising at least one nonionic group. The curable coating compositioncan then be applied to a substrate to form a curable coating and curedto form the coating.

The present invention further relates to a coating having a preselectedresistivity at a preselected pigment loading level comprising a resinand a modified pigment. The modified pigment comprises a pigment havingattached at least one organic group having the formula —X—I or —X—NI,wherein X, which is directly attached to the pigment, represents anarylene or heteroarylene group, an alkylene group, an aralkylene group,or an alkarylene group, I represents a non-polymeric group comprising atleast one ionic group or at least one ionizable group, and NI representa non-polymeric group comprising at least one nonionic group. A coatingcomprising the resin and said pigment has a resistivity at thepreselected pigment loading level that is lower than the resistivity ofthe coating comprising the resin and the modified pigment at saidpreselected pigment loading level.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the presentinvention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph which shows the surface resistivity of coatings andhow surface chemistry can be used for resistivity control.

FIG. 2, FIG. 3, and FIG. 4 are graphs which show the surface resistivityof coatings versus various features of the modified pigments. Differentorganic groups are shown in FIG. 3. FIG. 2 and FIG. 3 show the effect oftreatment level and FIG. 4 shows the effect of attachment level.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to curable coating compositions, curablecoatings, and coatings comprising modified pigments, and black matrixesthat can be formed therefrom.

The present invention relates to a curable coating composition, which,in one embodiment may be used to prepare the black matrix of the presentinvention, described in more detail below. The curable coatingcomposition comprises a vehicle, a curable resin, and at least onemodified pigment. The vehicle may be either an aqueous vehicle or anon-aqueous vehicle. While both aqueous and non-aqueous liquid vehiclescan be used, preferably the liquid vehicle is a non-aqueous vehicle.Examples include non-aqueous vehicles comprising butyl acetate,ethylcellosolve, ethylcellosolve acetate, butylcellosolve,butylcellosolve acetate, ethylcarbitol, ethylcarbitol acetate,diethyleneglycol, cyclohexanone, propyleneglycol monomethylether,propyleneglycol monomethylether acetate, lactate esters, dimethylformamide, methyl ethyl ketone, dimethylacetamide, and mixtures thereof.Aqueous solvents may also be added, including, for example, water andwater soluble alcohols.

The curable resin may be any resin known in the art. For example, theresin may be an epoxy bisphenol-A resin or an epoxy novolac resin. Theresin may also be an acrylic resin, a polyimide resin, a urethane resin,a polyester resin, or a gelatin. The resin is one that may be cured by avariety of known methods, including, for example, thermally or by anysource of radiation such as, for example, infrared or ultravioletradiation. In this way, the curable coating composition may bephotosensitive (i.e. may be cured by irradiation) or thermosensitive(i.e., may be cured by changing temperature, such as by heating). Whenthe resin is curable by irradiation, the curable coating composition mayfurther comprise a photoinitiator, which generates a radical onabsorbing light with the respective pigment.

The modified pigment used in the curable coating composition of thepresent invention comprises a pigment having attached at least oneorganic group. The pigment can be any type of pigment conventionallyused by those skilled in the art, such as black pigments and othercolored pigments including blue, black, brown, cyan, green, white,violet, magenta, red, orange, or yellow pigments. Mixtures of differentpigments can also be used. Representative examples of black pigmentsinclude various carbon blacks (Pigment Black 7) such as channel blacks,furnace blacks and lamp blacks, and include, for example, carbon blackssold under the Regal®, Black Pearls®, Elftex®, Monarch®, Mogul®, andVulcan® trademarks available from Cabot Corporation (such as BlackPearls® 2000, Black Pearls® 1400, Black Pearls® 1300, Black Pearls®1100, Black Pearls® 1000, Black Pearls® 900, Black Pearls® 880, BlackPearls® 800, Black Pearls® 700, Black Pearls® L, Elftex® 8, Monarch®1400, Monarch® 1300, Monarch® 1100, Monarch® 1000, Monarch® 900,Monarch® 880, Monarch® 800, Monarch® 700, Mogul® L, Mogul® E, Regal®250, Regal® 250R, Regal® 350, Regal® 350R, Regal® 330, Regal® 400,Vulcan® P, Vulcan® XC-72, Vulcan® XC-72R). Suitable classes of coloredpigments include, for example, anthraquinones, phthalocyanine blues,phthalocyanine greens, diazos, monoazos, pyranthrones, perylenes,heterocyclic yellows, quinacridones, and (thio)indigoids. Such pigmentsare commercially available in either powder or press cake form from anumber of sources including, BASF Corporation, Engelhard Corporation andSun Chemical Corporation. Examples of other suitable colored pigmentsare described in the Colour Index, 3rd edition (The Society of Dyers andColourists, 1982). Preferably the pigment is a carbon product, such ascarbon black. These pigments can also be used in combination with avariety of different types of dispersants in order to form stabledispersions.

The pigment may also be a multiphase aggregate comprising a carbon phaseand a silicon-containing species phase or a multiphase aggregatecomprising a carbon phase and a metal-containing species phase. Themultiphase aggregate containing the carbon phase and thesilicon-containing species phase can also be considered asilicon-treated carbon black aggregate and the multiphase aggregatecontaining a carbon phase and a metal-containing species phase can beconsidered to be a metal-treated carbon black aggregate as long as onerealizes that in either case, the silicon-containing species and/ormetal-containing species are a phase of the aggregate just like thecarbon phase. The multiphase aggregates do not represent a mixture ofdiscrete carbon black aggregates and discrete silica or metal aggregatesand are not silica coated carbon blacks. Rather, the multiphaseaggregates that can be used as the pigment in the present inventioninclude at least one silicon-containing or metal-containing regionconcentrated at or near the surface of the aggregate (but put of theaggregate) and/or within the aggregate. The aggregate, thus contains atleast two phases, one of which is carbon and the other of which is asilicon-containing species, a metal-containing species, or both. Thesilicon-containing species that can be a part of the aggregate is notattached to a carbon black aggregate like a silica coupling agent, butactually is part of the same aggregate as the carbon phase.

The metal-treated carbon blacks are aggregates containing at least acarbon phase and a metal-containing species phase. The metal-containingspecies include compounds containing aluminum, zinc, magnesium, calcium,titanium, vanadium, cobalt, nickel, zirconium, tin, antimony, chromium,neodymium, lead, tellurium, barium, cesium, iron, silver, copper, andmolybdenum. The metal-containing species phase can be distributedthrough at least a portion of the aggregate and is an intrinsic part ofthe aggregate. The metal-treated carbon black may also contain more thanone type of metal-containing species phase or the metal-treated carbonblack can also contain a silicon-containing species phase and/or aboron-containing species phase.

The details of making these multiphase aggregates are explained in U.S.patent application Ser. Nos. 08/446,141, filed May 22, 1995; 08/446,142,filed May 22, 1995; 08/528,895, filed Sep. 15, 1995; 08/750,017, filedNov. 22, 1996, which is a National Phase Application of PCT No. WO96/37547, filed May 21, 1996; 08/828,785, filed Mar. 27, 1997;08/837,493 filed Apr. 18, 1997; and 09/061,871 filed Apr. 17, 1998. Allof these patent applications are hereby incorporated in their entiretiesherein by reference.

A silica-coated carbon product can also be used as the particle, such asthat described in PCT Application No. WO 96/37547, published Nov. 28,1996. which is hereby incorporated in its entirety herein by reference.

The pigment can have a wide range of BET surface areas, as measured bynitrogen adsorption, depending on the desired properties of the pigment.For example, the pigment may be a carbon black having a surface area offrom about 10 to 600 m²/g, such as from about 20 to 250 m²/g and about20 to 100 m²/g. As known to those skilled in the art, a higher thesurface area will correspond to smaller primary particle size. Thepigment can also have a wide variety of primary particle sizes known inthe art. For example, the pigment may have a primary particle size ofbetween about 5 nm to about 100 nm, including about 10 nm to about 80 nmand 15 nm to about 50 nm. If, for example, a higher surface area for acolored pigment is not readily available for the desired application, itis also well recognized by those skilled in the art that the pigment maybe subjected to conventional size reduction or comminution techniques,such as ball or jet milling, to reduce the pigment to a smaller particlesize, if desired.

The pigment can also have a wide range of dibutylphthalate absorption(DBP) values, which is a measure of the structure or branching of thepigment. For example, the pigment may be a carbon black having a DBPvalue of from about 25 to 70 mL/100 g, including from about 30 to 50mL/100 g and from about 30 to 40 mL/100 g. In addition, the pigment mayhave a wide range of primary particle sizes, such as from about 10 to100 nm, including from about 15 to 60 nm. The preferred pigmentsapproach an essentially overall spherical geometry. Pigments with othershapes, such as needles and plates, may also be used.

The modified pigment has attached at least one organic group. In oneembodiment, the organic group has the formula —X—I. In anotherembodiment, the organic group has the formula —X—NI. The modifiedpigment may also comprise at least one organic group having the formula—X—I and at least one organic group having the formula —X—NI. Each ofthese groups will be described in more detail below. The modifiedpigments may be prepared using methods known to those skilled in the artsuch that organic chemical groups are attached to the pigment. Thisprovides a more stable attachment of the groups onto the pigmentcompared to adsorbed groups, e.g., polymers, surfactants, and the like.For example, the modified pigments can be prepared using the methodsdescribed in U.S. Pat. Nos. 5,554,739, 5,707,432, 5,837,045, 5,851,280,5,885,335, 5,895,522, 5,900,029, 5,922,118, and 6,042,643, and PCTPublication WO 99/23174, the descriptions of which are fullyincorporated herein by reference. Such methods provide for a more stableattachment of the groups onto the pigment compared to dispersant typemethods, which use, for example, polymers and/or surfactants.

The group X represents an arylene or heteroarylene group, an alkylenegroup, an aralkylene group, or an alkarylene group. X is directlyattached to the pigment and is further substituted with an I group or anNI group. Preferably, X represents an arylene or heteroarylene group,such as a phenylene, naphthylene, or biphenylene. When X represents analkylene group, examples include, but are not limited to, substituted orunsubstituted alkylene groups that may be branched or unbranched. Forexample, the alkylene group may be a C₁-C₁₂ group such as methylene,ethylene, propylene, or butylene, group. Most preferably, X is anarylene group.

The group X can be further substituted with other groups, such as one ormore alkyl groups or aryl groups. Also, the group X may be substitutedwith one or more functional groups. Examples of functional groupsinclude, but are not limited to, R, OR, COR, COOR, OCOR, carboxylates,halogens, CN, NR₂, SO₃H, sulfonates, sulfates, NR(COR), CONR₂, NO₂,PO₃H₂, phosphonates, phosphates, N═NR, SOR, NSO₂R, wherein R, which canbe the same or different, is independently hydrogen, branched orunbranched C₁-C₂₀ substituted or unsubstituted, saturated or unsaturatedhydrocarbons, e.g., alkyl, alkenyl, alkynyl, substituted orunsubstituted aryl, substituted or unsubstituted heteroaryl, substitutedor unsubstituted alkaryl, or substituted or unsubstituted aralkyl.

The group I represents a group comprising at least one ionic group or atleast one ionizable group. The group I may also comprise a mixture of anionic group and an ionizable group. The ionic group is either anionic orcationic and is associated with a counterion of the opposite chargeincluding counterions such as Na⁺, K⁺, Li⁺, NH₄ ⁺, NR′₄ ⁺, acetate, NO₃⁻, SO₄ ⁻², R′SO₃ ⁻, R′OSO₃ ⁻, OH⁻, and Cl⁻, where R′ represents hydrogenor an organic group such as a substituted or unsubstituted aryl and/oralkyl group. The ionizable group is one that is capable of forming anionic group in the medium of use. Anionizable groups form anions andcationizable groups form cations. Ionic groups include those describedin U.S. Pat. No. 5,698,016, the description of which is fullyincorporated herein by reference.

The anionic groups are negatively charged ionic groups that may begenerated from groups having ionizable substituents that can form anions(anionizable groups), such as acidic substituents. They may also be theanion in the salts of ionizable substituents. Representative examples ofanionic groups include —COO⁻, —SO₃ ⁻, —OSO₃ ⁻, —HPO₃ ⁻, —OPO₃ ⁻², and—PO₃ ⁻². Preferably, the anionic group comprises a counterion that is amonovalent metal salt such as a Na⁺ salt, a K⁺ salt, a Li⁺ salt. Thecounterion may also be an ammonium salt, such as a NH₄ ⁺ salt.Representative examples of anionizable groups include —COOH, —SO₃H,—PO₃H₂, —R′SH, —R′OH, and —SO₂NHCOR′, where R′ represents hydrogen or anorganic group such as a substituted or unsubstituted aryl and/or alkylgroup.

The cationic groups are positively charged ionic groups that may begenerated from ionizable substituents that can form cations(cationizable groups), such as protonated amines. For example, alkyl oraryl amines may be protonated in acidic media to form ammonium groups—NR′₂H⁺, where R′ represent an organic group such as a substituted orunsubstituted aryl and/or alkyl group. Cationic groups may also bepositively charged organic ionic groups. Examples include quaternaryammonium groups (—NR′₃ ⁺) and quaternary phosphonium groups (—PR′₃ ⁺).Here, R′ represents hydrogen or an organic group such as a substitutedor unsubstituted aryl and/or alkyl group. Preferably, the cationic groupcomprises an alkyl amine group or a salt thereof or an alkyl ammoniumgroup.

Preferably, the group I comprises at least one carboxylic acid group orsalt thereof, at least one sulfonic acid group or salt thereof, at leastone sulfate group, a least one alkyl amine group or salt thereof, or atleast one alkyl ammonium group. Since it is preferred that the group Xbe an arylene group, preferred attached organic groups having theformula —X—I include, but are not limited to, aryl carboxylic acidgroups, aryl sulfonic acid groups, or salts thereof. For example, theattached organic group may be a benzene carboxylic acid group, a benzenedicarboxylic acid group, a benzene tricarboxylic acid group, a benzenesulfonic acid group, or salts thereof. The attached organic group mayalso be a substituted derivative of any of these.

The group NI represents a group comprising at least one nonionic group,which is a group having no apparent charge. Examples of non-ionic groupsinclude, but are not limited to, alkyl groups (such as —R″), carboxylicacid esters (such as —COOR″ or —OCOR″), amides (such as —CONHR″,—CONR″₂, —NHCOR″, or —NR″COR″), alkylene oxides, glycols, alcohols,ethers (such as —OR″), ketones (such as —COR″), halogens, and nitrites.In the above formulas, R″ is a branched or unbranched alkyl or alkylenegroup having 1-20 carbon atoms. Thus, for example, the group NI attachedto X may be a methyl or ethyl ester of a carboxylic acid or may be anon-polymeric group comprising this ester. Since it is preferred that Xbe an arylene group, preferred attached organic groups having theformula —X—NI include, but are not limited to, aryl carboxylic acidesters, aryl carboxylic acid amides, or aralkyl groups, wherein theester group, amide group, and alkyl group has 1-20 carbon atoms. Forexample, the attached organic group may be a methyl or ethyl ester of abenzene carboxylic acid group, a benzene dicarboxylic acid ester group,or a benzene tricarboxylic acid ester group, or may be a methyl or ethylbenzene group.

Surprisingly, it has been found that modified pigments having attachedorganic groups that do not comprise polymeric groups may be used in thecurable coating compositions, curable coatings, and coatings of thepresent invention. Thus, for the purposes of the present invention, thegroup I and the group NI are non-polymeric groups, which means that,while the group I comprises at least one ionic or ionizable group andthe group NI comprises at least one nonionic group, these groups do notcomprise groups prepared by the polymerization of individual monomerunits. For example, the group I is not a polymeric group which comprisesat least one ionic or ionizable group and the group NI is not apolymeric group which comprises at least one nonionic group.Furthermore, the group I is not an ionic group that comprises apolymeric counterion. These modified pigments have been found to provideseveral advantages over modified pigments comprising polymeric groups,which are described in more detail below.

The amount of attached organic groups having the formula —X—I or —X—NIcan be varied in order to attain the desired performance attributes.This allows for greater flexibility in optimizing performanceproperties. Preferably, the total amount of attached organic groups isfrom about 0.001 to about 10.0 micromoles of organic group/m² surfacearea of pigment, as measured by nitrogen adsorption (BET method). Morepreferably, the amount of attached organic groups is between from about0.01 to about 5.0 micromoles/m² and most preferably is between fromabout 0.05 to 3.0 micromoles/m². In addition, the modified pigments mayfurther comprise additional attached organic groups. This can result infurther improved properties. However, when additional attached groupsare present, these are also non-polymeric groups.

In addition, mixtures of modified pigments can be used. Thus, thecurable coating composition may comprise two or more modified pigments,wherein each of the modified pigments has an attached organic grouphaving the formula —X—I or —X—NI. The two modified pigments shoulddiffer in the type of attached group, the amount of attached group, thetype of pigment, or combinations thereof. Thus, for example, twomodified pigments, each having an attached organic group comprisingdifferent groups I (such as one having an attached organic groupcomprising at least one carboxylic acid group or salt thereof and onehaving an attached organic group comprising at least one sulfonic acidgroup or salt thereof) may be used together. Also, two modifiedpigments, each comprising a different pigment (such as two carbon blackseach having different surface areas and/or structures) and having thesame attached organic group (such as one comprising at least onecarboxylic acid group) may be used together. In addition, a modifiedpigment having an attached organic group having the formula —X—I may beused in combination with a modified pigment having an attached organicgroup having the formula —X—NI. Other combinations of modified pigmentshaving attached —X—I and —X—NI groups can be used. None of the modifiedpigments used in combination comprise polymeric groups.

The modified pigment used in the curable coating composition of thepresent invention may also comprise the reaction product of a pigmentand a persulfate reagent. The pigment may be any of those describedabove, and the persulfate reagent is preferably a persulfate salt suchas ammonium persulfate, sodium persulfate, or potassium persulfate. Thereaction product may be prepared by any method known in the art but ispreferably prepared by a method comprising the steps of i) combining thepigment, persulfate reagent, and an aqueous medium (such as water or amixture of water and at least one water soluble solvent containinggreater than 50% water), optionally with an additional strong acidand/or a surfactant or dispersant (such as an anionic or nonionicstabilizer) to form a mixture; ii) heating the mixture; and iii)neutralizing the mixture to a pH greater than 7.0. The heating steppreferably occurs below 100° C., such as between about 40° C. and about90° C. and preferably for a duration of less than 24 hours, such asbetween about 2 hours and 24 hours. The method may further comprise thestep of heating after neutralizing the mixture, which preferably occursat temperatures higher than the first heating step, such as 20° C. to40° C. higher, and preferably for a duration between about 2 and 12hours. Preferably the modified pigment is prepared by a processdescribed in U.S. Patent Publication No. 2004-0103822, which isincorporated in its entirety by reference herein.

The curable coating composition may be formed using any method known tothose skilled in the art, including, for example, using high shearmixing. Furthermore, the compositions may be prepared using a dispersionof the modified pigment, such as a millbase. The amount of modifiedpigment can be between about 1% and 60% based on the total weight ofdispersion, and is preferably between about 5% to 30% by weight. Morepreferably, the amount of modified pigment is such that, when thecoating composition is used to form a curable coating and subsequentlycured, the resulting coating comprises greater than or equal to about 30wt % of the modified pigment based on the total weight of the coating.Preferably, the resulting coating comprises greater than or equal toabout 50 wt % of the modified pigment based on the total weight of thecoating and more preferably comprises between about 50 wt % and 80 wt %of the modified pigment based on the total weight of the coating.

The curable coating composition can be formed with a minimum ofadditional components (additives and/or cosolvents) and processingsteps. However, additives such as surfactants and cosolvents may also beincluded. For example, when a photosensitive resin is used, such asepoxy bisphenol-A or epoxy novolak, a photoinitiator can also be added.Monomers and/or oligomers may also be added.

The present invention further relates to a curable coating. Preferably,the curable coating is prepared from the curable coating composition ofthe present invention, which is described in more detail above. Thecurable coating comprises a curable resin and at least one modifiedpigment, preferably wherein the modified pigment comprises a pigmenthaving attached at least one organic group having the formula —X—I orX—NI. The curable resin and the modified pigment can be any of thosedescribed in more detail above. The curable coating can be aphotosensitive coating, resulting in the formation of a coating byirradiating the curable coating, or a thermosensitive coating, in whicha coating is formed by thermal treatment of the curable coating. Forthis aspect of the present invention, the curable coating comprises asufficient amount of modified pigment such that, when cured to form acoating, the resulting coating comprises greater than or equal to about30 wt %, preferably greater than or equal to 50 wt %, and morepreferably between about 50 wt % and about 80 wt %, of the modifiedpigment based on the total weight of the coating.

The present invention further relates to a coating. Preferably, thecoating is prepared from the curable coating of the present invention,which is described in more detail above. In one embodiment, the coatingcomprises a resin and at least one modified pigment, wherein themodified pigment is any of those described in more detail above. Themodified pigment is present in an amount of greater than or equal toabout 30 wt %, preferably greater than or equal to 50 wt %, and morepreferably between about 50 wt % and about 80 wt %, of the modifiedpigment based on the total weight of the coating.

It has surprisingly been found that the curable coating compositions andcurable coatings of the present invention may be used to prepare curedcoatings that comprise pigments at relatively high levels, such as thosedescribed above, compared to levels found in conventional coatings.Also, since the attached organic group is non-polymeric, the percentcarbon content (by weight) of the pigment used in the coating may alsobe much higher (generally about 97% carbon) compared to coatingsprepared with pigments having attached polymeric groups or coated withpolymers. This enables the preparation of coatings and black matrixes,described in more detail below, having improved overall properties,including improved balance of electrical properties, such as volumeresistivity, and optical density. Volume resistivity is a measure of theability of a material to prevent the conduction of electricity and canbe measured using a variety of techniques known in the art including,for example, the method defied in ASTM procedure D257-93. Opticaldensity (OD) is a measure of the opacity of a material and is typicallymeasured using a densitometer. OD is dependent on several factors,including the thickness of the film. The coating of the presentinvention can have a volume resistivity of greater than or equal to 10¹²ohm-cm, preferably 10¹³ ohm-cm and further may have an optical densityof greater than or equal to 3, preferably greater than or equal to 4,and more preferably greater than or equal to 5, at a 1 micron thickness.Also, the coating of the present invention can have a volume resistivityof between 10⁶ and 10⁸ ohm-cm and may further have an optical density ofgreater than or equal to 4, more preferably between 4 and 5, at a 1micron thickness. The coatings of the present invention may also havesimilar electrical properties (such as resistivity) at greater filmthicknesses, including, for example, 10-100 micron thickness, dependingon the application of the coating.

Performance will depend on a variety of factors which may be controlledin accordance with certain embodiments of the present invention,including treatment level and pigment type. For example, it hassurprisingly been found that coatings comprising a resin and at leastone modified pigment, which comprises a pigment having attached at leastone organic group, have improved electrical properties compared tocoatings comprising the same resin and the same pigment, without theattached organic group. This is shown in general in FIG. 1 and morespecifically in FIGS. 2-4. Each of these is discussed in more detailbelow.

In general, the loading level of a specific carbon black effects thesurface resistivity of a coating containing that carbon black.Initially, at low loadings, the surface resistivity remainssubstantially constant with increasing amounts of carbon black. Athigher levels, a transition occurs in which enough pigment is presentthat a substantial decrease in resistivity occurs. This is oftenreferred to as the percolation threshold. Levels of pigment in excess ofthis threshold have very little effect on the resistivity of thecoating. In general, most carbon blacks exhibit similar percolationperformance. Thus, carbon black percolation curves are very similar,regardless of the type of carbon black, with the exception that thepercolation point (i.e., the loading of carbon black in which thesurface resistivity decreases) is different. This is shown by a shiftingof the percolation curve.

FIG. 1 shows representative percolation curves for three types ofcoatings. For the purposes of this representation, each coatingcomprises the same resin but a different carbon black. The carbon blackrepresented by percolation curve C, which is representative of thepresent invention, is a modified carbon black pigment having attached atleast one organic group. The carbon blacks represented by percolationcurves A and B are carbon black pigments that have not been modified tohave an attached organic group. Also shown is a preselected targetsurface resistivity and preselected target loading level (wt % C)desired for a coating.

The carbon black represented by curve A does not produce a coatinghaving the targeted resistivity at any carbon black loading levels. Inorder to produce a coating having this targeted resistivity, a differentcarbon black would be needed. Typically, in the art, this isaccomplished using a carbon black that has a different morphology thanthat of the carbon black of curve A. Thus, for example, a carbon blackhaving a structure (DBP) that is different from that represented bycurve A would have to be found in order to produce a coating having thetargeted performance. This is shown by curve B. As shown in FIG. 1,curve B is similar to curve A but is shifted such that that higherlevels (wt % C) of the carbon black of curve B are needed to producecoatings having the targeted surface resistivity. As shown, while thecarbon black of curve B does produce a coating having the targetedperformance, choosing an alternative carbon black having a differentmorphology may have several disadvantages, including, for example, cost,processing effects, and the like.

Furthermore, as shown in FIG. 1, the target surface resistivity may fallon the steepest point of the percolation curve. From a practicalperspective, manufacturing this coating would require tight controls onthe carbon black loading since small changes in loading would have alarge effect on the observed resistivity. This is generally true forcarbon black-containing coatings, which typically have a surfaceresistivity between about 10⁵ and 10¹² ohm/square.

In order to produce a coating having the preselected performance shownin FIG. 1 without changing morphology, an alternative approach isneeded. In the present invention, it has surprisingly been found thatthe resistivity of a coating can be improved if the coating comprises atleast one modified pigment comprising a pigment having attached at leastone organic group. It has also been found that coatings having apreselected surface resistivity can be produced using a carbon blackthat would not have otherwise produced the desired performance. This isshown by curve C, which represents a modified carbon black pigment,wherein the carbon black pigment that has been modified is the carbonblack represented by curve A. The unmodified carbon black of curve A, asdiscussed above, does not meet the preselected resistivity performance.However, the carbon black of curve A modified to have attached at leastone organic group, shown by curve C, would produce a coating having thedesired performance.

Thus, the resistivity of a coating comprising a modified carbon blackpigment has been found to be higher than the resistivity of coatingscontaining the same but unmodified pigment. As shown by therepresentative percolation curves in FIG. 1, the resistivity of a filmcontaining a given carbon black can be increased by changing the surfacechemistry of that carbon black, in accordance with the presentinvention. The percolation curve for a given carbon black can also bechanged through surface chemistry in accordance with the invention. Ithas surprisingly been found that resistivity increases with treatmentlevel in general, particularly at higher loading levels. As a result,through the use of the present invention, the percolation curve may beshifted such that a preselected resistivity may occur away from thesteepest part of the curve. Thus, small changes in loading do not have alarge effect on resistivity.

Thus, it has been found that a preselected or desired targetresistivity, particularly at a target loading, can be attained using amodified pigment. The modified pigment comprises a pigment havingattached at least one organic group, and this pigment may be a pigmentthat could not have previously been used to produce a coating having thepreselected resistivity, particularly at a specified loading.Additionally, changing morphology may provide optimized coatingproperties.

Additionally, it has been found that the amount of attached organicgroups can be varied in order to attain the desired performance. This isshown in FIGS. 2-4. FIG. 2 shows the effect of treatment level (i.e.,the amount of reagent added to prepare the modified pigment) on thesurface resistivity of coatings comprising a resin (Joncryl 611) atvarious levels of the modified pigment comprising a pigment (Regal® 250carbon black) having attached at least one organic group (—C₆H₄—SO₃Na).As can be seen in FIG. 2, in general, as the treatment level increases,the surface resistivity increases. The effect is more clearly seen atthe higher loading levels, particularly above the percolation threshold,especially a coating comprising 83.3 wt % carbon, which corresponds tothe millbase. Furthermore, coatings prepared using a modified carbonblack at higher loading levels may have resistivities similar to thoseprepared using an unmodified carbon black at significantly lowerloadings. FIG. 3 shows the resistivity of coatings prepared frommillbases comprising a modified pigment which is a pigment (Regal® 250carbon black) having attached at least one organic group (either a—C₆H₄—CO₂Na group or a —C₆H₄—CH₂CH₂OH group). In FIG. 3, the loadinglevel of carbon black is 83.3 weight %, and, as can be seen, increasingthe treatment level increases the resistivity of the coating. FIG. 4shows the same coatings as in FIG. 3 (with the modified pigmentcomprising a pigment having attached at least one —C₆H₄—CO₂Na group), inwhich the amount of attached groups has been measured by TGA. As FIG. 4shows, as the amount of attached groups (attachment level) increases, asrepresented by the measured volatile content, surface resistivityincreases. It has surprisingly been found that surface resistivity canbe changed 8 orders of magnitude by changing the amount of attachedgroups, and that a surface resistivity as high as at least 10¹²ohm/square can be achieved using a pigment having a volatile content ofless than 3%.

Thus, FIG. 1-4 exemplify an embodiment of the present invention, whichis a method of controlling the resistivity of a coating comprising aresin and a pigment. The method comprises the step of preparing acurable coating composition comprising a vehicle, a curable resin, andat least one modified pigment. The modified pigment comprises thepigment having attached at least one organic group having the formula—X—I or —X—NI, wherein X, which is directly attached to the pigment,represents an arylene or heteroarylene group, an alkylene group, anaralkylene group, or an alkarylene group, I represents a non-polymericgroup comprising at least one ionic group or at least one ionizablegroup, and NI represent a non-polymeric group comprising at least onenonionic group. The curable coating composition can then be applied to asubstrate to form a curable coating and cured to form the coating. Thesefigures also show an embodiment of the coating of the present invention,having a preselected resistivity at a preselected pigment loading levelcomprising a resin and a modified pigment as described above. A coatingcomprising the resin and said pigment, used to prepare the modifiedpigment, has a resistivity at the preselected pigment loading level thatis lower than the resistivity of the coating comprising the resin andthe modified pigment at said preselected pigment loading level.

FIG. 4 further exemplifies an embodiment of the coating of the presentinvention which comprises a resin and a modified pigment describedabove. The modified pigment has a volatile content of less than 3%,preferably between about 0.5% and about 3%, and the coating has aresistivity of between 10⁶ and 10¹³ ohm/square. Preferably the modifiedpigment has a volatile content of between about 1.0% and about 3.0%, andthe coating has a resistivity of between 10⁸ and 10¹³ ohm/square. Thus,it has surprisingly been found that coating compositions having highresistivity (such as greater than 10⁸ ohm/square, preferably greaterthan 10¹⁰ ohm/square) can be produced using a pigment having a lowvolatile content, such as less than 3%.

The present invention further relates to a black matrix which may beused in, for example, for a color filter in a liquid crystal displaydevice. The black matrix can be formed using any method known in theart. For example, the black matrix may be formed by applying a curablecoating composition comprising a modified carbon product onto asubstrate, curing the resulting curable coating imagewise, anddeveloping and drying the cured coating. Preferably, the black matrix isprepared from the curable coating composition, curable coating, and/orthe coating of the present invention, each of which is described in moredetail above.

Volume resistivity and optical density are important properties forblack matrix materials, and are described in more detail above. Sincethe black matrixes of the present invention are preferably formed fromthe curable coating compositions of the present invention, which is usedto form a cured coating of the present invention, the black matrix canhave the performance properties (volume resistivity and optical density)described above in relationship to the coating. In addition, the amountof the attached organic groups of the modified carbon product in theblack matrixes of the present invention can be varied in order to attaindifferent desired overall performance attributes. Furthermore, theamount of modified carbon product can be varied and will depend on thetype of carbon product and the amount of attached groups. The amount ofmodified carbon product in the black matrix of the present invention isgreater than or equal to 30 wt %, preferably greater than or equal to 50wt %, and more preferably between about 50 wt % and 80 wt %.

The present invention further relates to a color filter which can beused in combination with a black matrix and, in particular, the blackmatrix of the present invention. The color filter may be formed usingany method known in the art and, in particular using a method similar tothat for the black matrix described above. For this application,modified pigments would be used which correspond in color to the colorsneeded for the pixels of the display device.

The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature.

EXAMPLES Example 1 Preparation of a Modified Pigment

550 g of Regal® 250R carbon black (commercially available from CabotCorporation), 31.5 g of sulfanilic acid, and 1000 grams of DI water wereadded to a plow mixer that was jacket-heated to 60° C. A solution of12.6 g of sodium nitrite in 100 g of DI water was prepared, and this wasadded to the mixture in the plow mixer. The reaction mixture was mixedat approximately 50 rpm at 60° C. for 2 hours and then allowed to cooldown to room temperature. The resulting dispersion of carbon black wasdiluted to 15% solids and processed by diafiltration with DI watermake-up for 7 volumes. The final dispersion was dried in a 75° C. ovenovernight and then ground using a lab blender to produce a powder of amodified pigment having attached benzenesulfonic acid groups.

Examples 2A and 2B Preparation of Millbase

Millbases were prepared using the modified carbon black of Example 1(Example 2A) and Regal® 250R carbon black (Example 2B). The materialsand the amounts used are shown in Table 1. Solsperse 32500 is apolymeric dispersant commercially available from Noveon. The componentswere milled using a Skandex lab shaker for 2 hours. The mean volumeparticle size of the pigments in the millbases were measured and foundto be comparable to the aggregate size of base carbon black.

TABLE 1 Millbase Example 2A Example 2B Pigment Example 1 Regal ® 250RAmount of pigment  15 g  15 g Dispersant Solsperse 32500 Solsperse 32500Amount of dispersant 7.5 g 7.5 g PGMEA 52.5 g  52.5 g 

Examples 3 Preparation of Letdowns

Each of the millbases of Example 2 were letdown with a 20 wt % solutionof Joncryl 611 (commercially available from Johnson Polymers) in PGMEAto prepare coating compositions containing 30%, 40%, 50%, 60%, 70%carbon black by weight on a solvent-free basis. These are very highlevels compared to conventional coating compositions. The compositionsare shown in Table 2 below.

TABLE 2 Coating Compositions Amount Example # Millbase of pigment Ex3A-1 Ex 2A 30% Ex 3B-1 Ex 2B 30% Ex 3A-2 Ex 2A 40% Ex 3B-2 Ex 2B 40% Ex3A-3 Ex 2A 50% Ex 3B-3 Ex 2B 50% Ex 3A-4 Ex 2A 60% Ex 3B-4 Ex 2B 60% Ex3A-5 Ex 2A 70% Ex 3B-5 Ex 2B 70%

Example 4 Preparation of Coatings

The coating compositions of Example 3 were spin coated onto glass wafersto form coatings, and properties of these coatings were measured.Optical density was measured using a X-Rite 361T TransmissionDensitometer, and the thickness was measured using a KLA Tencor AlphaStep 500 Surface Profilometer. The surface resistivity of the coatingswas measured using a Keithley Model 6517 Electrometer/High ResistanceMeter.

Performance properties of each of the coatings are shown in Tables 3 and4 below.

TABLE 3 Electrical properties Example # Surface resistivity (Ω/square)Ex 3A-1 1.04 × 10¹² Ex 3B-1 2.45 × 10¹¹ Ex 3A-2 7.17 × 10¹¹ Ex 3B-2 6.97× 10¹¹ Ex 3A-3 2.59 × 10¹¹ Ex 3B-3 5.58 × 10¹⁰ Ex 3A-4 9.80 × 10¹⁰ Ex3B-4  3.6 × 10⁷   Ex 3A-5 1.47 × 10⁸   Ex 3B-5 1.72 × 10⁵  

TABLE 4 Optical properties Example # OD (1μ thickness) Ex 3A-1 1.75 Ex3B-1 1.84 Ex 3A-2 2.43 Ex 3B-2 2.57 Ex 3A-3 3.17 Ex 3B-3 3.29 Ex 3A-43.52 Ex 3B-4 4.21 Ex 3A-5 4.48 Ex 3B-5 4.90

These results show that coatings comprising modified pigments asdescribed herein have higher surface resistivity compared to those usingconventional pigments. These coatings also maintain a high opticaldensity. It would be expected that these coatings would also have highervolume resistivity compared to coatings comprising conventional pigmentsat the same coating thickness.

While these examples use a resin that is not curable, it would beexpected that similar performance would result if a curable resin, suchas a photosensitive or thermosensitive resin, were used. Therefore,these coatings could be used as a black matrix.

Example 5 Preparation of a Coating

A coating was prepared using a procedure similar to that described inExample 4 but using a composition prepared by milling a combination ofthe modified pigment of Example 1 (6 g), 30.8 g of 20% solution ofJoncryl 611 in PGMEA, and 23.2 g of PGMEA in a paint shaker for 8 hours.The resulting coating, having 50% by weight pigment, was found to havean optical density of 3.0 at 1μ thickness. Volume resistivity was foundto be 1.8×10¹⁴ ohm-cm.

Properties of this coating can be compared with those of similarcoatings (50% CB) obtained using modified pigments comprising the samebase pigment but having attached polymeric groups, and mixed withJoncryl 611 in PGMEA (described in Proceedings of IDW'02, #FMC4-2, p.425 by E. Step). These coatings were found to have an optical density of3.0 at 1μ thickness and a volume resistivity of 7.0×10¹³ ohm cm.Therefore, a coating comprising a modified pigment as described hereinhas better resistivity properties while maintaining optical densitycompared to a modified pigment comprising attached polymeric groups.

Examples 6-8 Preparation of Coatings

Modified pigments were prepared using the procedure described in Example1, with different amounts of sulfanilic acid and the same ratio ofsodium nitrite to sulfanilic acid. Millbases were then prepared usingthese modified pigments, following the procedure described for Examples2A and 2B, which were then letdown using the procedure described forExample 3 to prepare coating compositions containing various loadings ofcarbon black. The treatment levels used for each example, calculatedfrom the amount of sulfanilic acid and the surface area of the carbonblack (Regal® 250R carbon black), are shown in Table 5 below, which alsoincludes the treatment levels of the pigments used for Examples 3A and3B. The compositions are shown in Table 6 below, along with those ofExamples 3A and 3B.

TABLE 5 Treatment Levels Example # Pigment Treatment Level Ex 3A 6μmoles/m² Ex 6 3 μmoles/m² Ex 7 2 μmoles/m² Ex 8 1 μmoles/m² Ex 3B 0μmoles/m²

Coatings were then prepared using the procedure described in Example 4,and the surface resistivity of each coating was measured. The coatingscomprising 83.3 wt % carbon correspond to the millbases. Results areshown in Table 6 below. This is also shown graphically in FIG. 2.

TABLE 6 Surface Resistivities (Ω/square) % Pigment Ex 3A Ex 6 Ex 7 Ex 8Ex 3B 10 8.35 × 10¹¹ 20 1.67 × 10¹² 30 1.04 × 10¹² 3.58 × 10¹¹ 8.84 ×10¹² 5.05 × 10¹¹ 2.45 × 10¹¹ 40 7.17 × 10¹¹ 1.49 × 10¹¹ 4.24 × 10¹² 6.42× 10¹¹ 6.97 × 10¹¹ 50 2.59 × 10¹¹ 2.23 × 10¹¹ 2.17 × 10¹² 2.16 × 10¹¹5.58 × 10¹⁰ 60  9.8 × 10¹⁰ 5.08 × 10¹¹ 6.92 × 10¹⁰ 4.69 × 10¹⁰ 3.61 ×10⁷ 70 1.47 × 10⁸ 3.40 × 10⁸ 1.67 × 10⁶ 1.89 × 10⁵ 1.72 × 10⁴ 83.3 5.53× 10⁷ 1.23 × 10⁷ 9.47 × 10⁵ 5.70 × 10⁴ 4.59 × 10³

These results show that, for coatings prepared from the coatingcompositions of the present invention comprising modified pigments,treatment level effects resistivity. In general, as the treatment levelincreases, the surface resistivity increases. This effect is moreclearly seen at the higher loading levels. Furthermore, coatingsprepared using a modified carbon black at higher loading levels may haveresistivities similar to those prepared using an unmodified carbon blackat significantly lower loadings. It would be expected that similartrends would be seen comparing volume resistivity at equivalent coatingthickness.

While these examples use a resin that is not curable, it would beexpected that similar performance would result if a curable resin, suchas a photosensitive or thermosensitive resin, were used. Therefore,these coatings could be used as a black matrix.

Example 9

Coatings were prepared from millbases, which were prepared using theprocedure similar to that described in Examples 6-8. These coatingscomprise 83.3 wt % carbon black. Example 9A is a comparison coatingcomprising a conventional carbon black. Examples 9B-9F are coatings ofthe present invention comprising modified carbon blacks. For Examples9A-9F, the modified carbon blacks were prepared using a proceduresimilar to that described in Example 1, except using 4-aminobenzoic acid(PABA) instead of sulfanilic acid, and using a smaller scale mixerrather than the plow mixer. The amount of PABA used for each of theseexamples correspond to the treatment levels (added levels of PABA) shownin Table 7 below. Also, for each example, the percent volatiles (totalamount of volatiles), measured by TGA, for the carbon blacks used areshown.

TABLE 7 Treatment Surface Film Example Level % Resistivity Thickness #(μmoles/m²) Volatile (Ω/square) (μm) 9A 0 0.10% 4.00 × 10³ 1.065 9B 10.17% 3.30 × 10⁴ 0.984 9C 2 0.49% 3.70 × 10⁵ 0.965 9D 6 1.40% 2.00 × 10⁸0.936 9E 10 2.03% 2.00 × 10⁹ 0.892 9F 40 2.78%  2.92 × 10¹¹ 0.898

The surface resistivity and film thickness of each coating was measuredas described in Example 4, and these results are also shown in Table 7above as well as graphically in FIG. 3 (treatment level and surfaceresistivity) and FIG. 4 (% volatiles and surface resistivity).

Also shown in FIG. 4 are surface resistivity values for coatingsprepared using a modified carbon black having attached phenethyl alcoholgroups, which were prepared using a procedure similar to that describedin Example 1 with the exception that 4-aminophenethyl alcohol was usedin place of sulfanilic acid. For coatings containing 6, 10, and 20μmoles/m² treatment levels of 4-aminophenylethyl alcohol, surfaceresistivity values of 1.29×10⁷, 1.05×10⁸, and 1.03×10⁹ Ω/square(respectively) were found.

These results show that, for coatings prepared from the coatingcompositions of the present invention comprising modified pigments, asthe treatment level increases, the surface resistivity increases. Thiseffect can be seen for both treatment types. Similar trends are seencomparing % volatile values, which can be considered an indication ofattachment level. It has surprisingly been found that a modified pigmenthaving a low volatile content, such as those shown above, can be used toproduce a coating having high resistivities. It would be expected thatthese coatings would also have increasingly higher volume resistivitywith increasing treatment level and % volatiles, at the same coatingthickness.

While these examples use a resin that is not curable, it would beexpected that similar performance would result if a curable resin, suchas a photosensitive or thermosensitive resin, were used. Therefore,these coatings could be used as a black matrix.

The foregoing description of preferred embodiments of the presentinvention has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Modifications and variationsare possible in light of the above teachings, or may be acquired frompractice of the invention. The embodiments were chosen and described inorder to explain the principles of the invention and its practicalapplication to enable one skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto, and theirequivalents.

1. A black matrix formed by applying a curable coating composition ontoa substrate to form a curable coating, curing the curable coatingimagewise to form a cured coating, and developing and drying the curedcoating, wherein the curable coating composition comprises a vehicle andat least one modified pigment comprising a pigment having attached atleast one organic group having the formula —X—I, wherein X, which isdirectly attached to the pigment, represents an arylene or heteroarylenegroup, or an alkylene group, and I represents a non-polymeric groupcomprising at least one ionic group or at least one ionizable group, andwherein the cured coating comprises greater than or equal to about 30 wt% of the modified piggment based on the total weight of the curedcoating.
 2. The black matrix of claim 1, wherein X represents an aryleneor heteroarylene group, or an alkylene group having 12 carbons or less.3. The black matrix of claim 1, wherein X is an arylene group.
 4. Theblack matrix of claim 1, wherein I comprises at least one carboxylicacid group or salt thereof, at least one sulfonic acid group or saltthereof, at least one alkyl sulfate group, at least one alkyl aminegroup or salt thereof, or at least one alkyl ammonium group.
 5. Theblack matrix of claim 4, wherein the salt is a Na⁺ salt, a K⁺ salt, aLi⁺ salt, or a NH₄ ⁺ salt.
 6. The black matrix of claim 1, wherein theorganic group is an aryl carboxylic acid salt group or an aryl sulfonicacid salt group.
 7. The black matrix of claim 1, wherein the curablecoating is a photosensitive coating and the coating is formed byirradiating the curable coating.
 8. The black matrix of claim 7, whereinthe curable coating composition comprises a photocurable resin andoptionally further comprises at least one photoinitiator.
 9. The blackmatrix of claim 1, wherein the curable coating is a thermosensitivecoating and the coating is formed by thermal treatment of the curablecoating.
 10. The black matrix of claim 1, wherein the cured coatingcomprises greater than or equal to about 50 wt % of the modified pigmentbased on the total weight of the cured coating.
 11. The black matrix ofclaim 1, wherein the cured coating comprises between about 50 wt % and80 wt % of the modified pigment based on the total weight of the curedcoating.
 12. The black matrix of claim 1, wherein the coating has avolume resistivity of greater than or equal to 10¹² ohm-cm.
 13. Theblack matrix of claim 12, wherein the coating further has an opticaldensity of greater than or equal to 3 at a 1 micron thickness.
 14. Theblack matrix of claim 1, wherein the coating has a volume resistivity ofbetween 10⁶ and 10⁸ ohm-cm.
 15. The black matrix of claim 14, whereinthe coating further has an optical density of greater than or equal to 4at a 1 micron thickness.
 16. The black matrix of claim 1, wherein thevehicle is a non-aqueous vehicle.
 17. The black matrix of claim 1,wherein the vehicle comprises propyleneglycol monomethyl ether acetate.18. The black matrix of claim 1, wherein the vehicle is an aqueousvehicle.
 19. The black matrix of claim 1, wherein the curable coatingcomposition comprises at least two modified pigments, wherein themodified pigments are not the same.
 20. The black matrix of claim 19,wherein at least one of the modified pigments comprises at least onecarboxylic acid group or salt thereof and wherein at least one of themodified pigments comprises at least one sulfonic acid group or saltthereof.
 21. The black matrix of claim 1, wherein the modified pigmentfurther has attached at least one organic group having the formula—X—NI, wherein NI represents a non-polymeric group comprising at leastone nonionic group.
 22. The black matrix of claim 21, wherein thenonionic group is an alkyl group, a carboxylic acid ester, an amide, analkylene oxide, a glycol, an alcohol, an ether, a ketone, a halogen, ora nitrile.
 23. The black matrix of claim 21, wherein the nonionic groupis an aryl carboxylic acid ester, an aryl carboxylic acid amide, or anaralkyl group.
 24. A black matrix formed by applying a curable coatingcomposition onto a substrate to form a curable coating, curing thecurable coating imagewise to form a cured coating, and developing anddrying the cured coating, wherein the curable coating compositioncomprises a vehicle and at least one modified pigment comprising apigment having attached at least one organic group having the formula—X—NI, wherein X, which is directly attached to the pigment, representsan arylene or heteroarylene group, or an alkylene group, and NIrepresents a non-polymeric group comprising at least one nonionic group,and wherein the cured coating comprises greater than or equal to about30 wt % modified pigment based on the total weight of the cured coating.